Speaking in Code – New Building Code Requirements for Structural Concrete (ACI 318-14)

As we age – and as we reach a certain age – we tend to put on weight. We may fight against it, but the unyielding pressures of time and gravity eventually get to most of us.

Did you also know that those same laws of inevitability also apply to regulations such as those published by the American Concrete Institute (ACI)? It’s true, and the evidence is in the picture to the right. That svelte booklet on the bottom? That is the 1971 version of the concrete codes. The corpulent tome on top? That is what the regulations look like now. One key difference between people and the code, however, is that unlike in people, not only has the size grown, but where exactly key elements are located within the body has shifted about rather dramatically.

The latest change in ACI regulations comes with the publishing of the “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14)”. If you work with concrete, it is important that you understand the changes that have been made because these changes have already been adopted by the 2015 International Building Code (IBC). As a result, whenever the 2015 IBC Code is adopted by a local jurisdiction, ACI 318-14 will be the law within that jurisdiction. Maryland and South Carolina, have already adopted these standards, and more states will eventually move in this direction.

The new concrete code (ACI 318-14) has undergone a complete restructuring and represents the first reorganization of the concrete code since 1971 (45 years). Included in the countless organizational changes, however, are numerous technical changes.

The Reorganization

The new ACI 318-14 is a “member-based” document, and the embracing of this concept is the primary reason for the entire reorganization. Under this approach, each chapter is devoted to a particular member type, such as beam or column, so the user can find all the requirements necessary to design that particular member type. Theoretically, this methodology will eliminate the need to flip through several chapters in order to comply with all of the required design requirements for a specific structural member (which was necessary with the old format).

The major challenge of this concept was to determine where to place the design information that applies to multiple member types. To repeat essentially the same information in multiple chapters made little sense, so this design information is compiled in “toolbox chapters”. The specific design information in the toolbox chapters is then referenced from the member-based chapters.

Below is a chart which outlines how the chapters have been restructured in the new code. It may take us all a little while to figure out where everything is. ACI 318-14 is very clear on the fact that ACI 318 is not a construction specification and defers to other ACI standards, the contract documents, and the general building code (such as Chapter 17, Table 1705.3 of IBC).

Click on the chart to enlarge.

There are a few things that stand out:

In the previous code, information regarding concrete materials, minimum water-cement ratios, and testing/inspection criteria could always be found in Chapters 3, 4 or 5 of ACI 318. With the advent of ACI 318-14, this is no longer the case. Most, but not all, of this information is now located in Chapters 19 and 26.

In the old code (ACI 318-11), the installation and testing/inspection of concrete anchors were addressed in Appendix D, “Anchoring to Concrete”. In the new code (ACI 318-14), Appendix D is gone as well as all other Appendices. That is right, there are no appendices in ACI 318-14. The entire 50-page Appendix D on concrete anchors is now located in Chapter 17 of ACI 318-14 and is entitled “Anchoring to Concrete”.

Chapter 20, “Strength Evaluation of Existing Structures” in the old code is now Chapter 27 in the new concrete code (ACI 318-14). The provisions of this chapter applies to strength evaluation of existing structures by analytical means or by load testing has been transferred for the most part intact.

Chapter 26, “Construction Documents and Inspection” may represent the single largest addition to the concrete code; it did not exist in the old code and is new in ACI 318-14. Except for the inspection requirements of section 26.13, the provisions of this chapter are organized by design information and compliance requirements. Compliance requirements are general provisions that provide a minimum acceptable level of quality for construction of the work.

Technical Changes

Two chapters that encompass most of technical changes from the old code to the new are chapters 18, “Earthquake Resistant Structures” and chapter 19, “Concrete: Design and Durability Requirements”. These chapters should be reviewed carefully because there are many changes set forth as part of the transition from old to new. Some of the class identifications of exposure categories have been changed and some of the maximum water-cement ratios and compressive strength values have changed for the “S” classes of concrete. Section 19.3.2.2 has new verbiage that mandates that air content tests be performed at the readymix concrete truck. Previously, this information could only be found in ASTM C 172, “Standard Practice of Sampling Freshly Mixed Concrete”.

Final Thoughts

As you review ACI 318-14, you should read the NEW section 1.5. This section tells the user how to properly interpret ACI 318 provisions. The intent of the commentary is to assist the user and enhance the process of understanding the building code. However, the commentary is not a part of the code and does not provide binding requirements.

If you have any questions about the elements of the code discussed in this edition of Speaking in Code, or any other code-related question, please feel free to contact Alan Tuck, F&R’s Executive Director for Code Compliance and Training.